(1) Field of the Invention
The present invention relates to improved fume hoods or ventilated workstations having a floor opening through which the upper end of a container is inserted into the hood enclosure, and in particular to a method and apparatus for securing a flexible sealing membrane around the floor opening.
(2) Description of the Prior Art
Fume hoods or vented workstations are used in laboratories and other environments to manipulate materials that might generate noxious or dangerous gases or fumes without releasing the materials or components or fumes therefrom into the work environment. Generally, these workstations are comprised of an enclosure or chamber in which materials are handled, and means for drawing air through a front opening in the enclosure. The operator also uses this front opening as the means of access into the enclosure. The enclosure also includes an exhaust opening, frequently communicating with a filter, to remove contaminants from air exhausted from the chamber.
When working with hazardous or toxic material, there is frequently a need to remove materials from a container, to insert materials into a container, or to transfer material from one container to another container. Some of these containers, which may be carboys, drums, or the like, are quite large and difficult to maneuver. Therefore, placement of one or more of these containers into a fume hood to prevent escape of hazardous materials into the surrounding environment, as well as their subsequent removal, and the insertion or transfer of materials to or from these containers, can be difficult, if not impossible.
Commonly assigned U.S. Pat. No. 6,431,975 to Ryan, incorporated herein by reference in its entirety, provides an apparatus addressing this need. The Ryan fume hood is comprised of an enclosure that includes at least one container-receiving opening in the floor of the enclosure. The enclosure is supported so that a large container having a top opening through which material can be added to, or removed from, can be positioned beneath the enclosure and then raised upwardly, so that the upper section of the container projects through the opening and into the enclosure.
The operator can then open the container from within the enclosure, remove or add material, and then close the container. The container is then lowered to separate the container from the enclosure. As a result, the opening into the container is at all times within the fume hood enclosure when the container is open, thereby preventing hazardous materials from escaping from outside the hood enclosure. As used herein, the term “hazardous” is broadly intended to include all materials, whether in powder, liquid or gaseous form, where escape beyond a confined area is undesirable, and the term “container” is intended to include all containers for such materials.
In order to create a flexible seal between the container and the floor when the container is inserted through the opening, thereby preventing leakage of gases into or out of the enclosure, an annular flexible sealing member or membrane is positioned around the opening, with the inner diameter of the membrane being less than the diameter of the opening. In the Ryan apparatus, this membrane is held in place by rings that clamp the membrane to the floor.
Attachment of membranes around the hood floor opening with clamped rings as described by Ryan can be time-consuming and achieving a complete seal can be difficult. Moreover, the rings and clamps may become contaminated during use of the fume hood, requiring decontamination or disposal. Therefore, there is a need for an apparatus and method for quickly and securely attaching membranes around a floor opening in fume hoods of the type described in the Ryan patent, and in particular to a means of membrane attachment that eliminates the use of rings and clamps requiring decontamination or disposal.